System and Method of Determining Differential State of a Vehicle

The present disclosure generally relates to a system and method of determining a differential state of a vehicle. More specifically, the present disclosure relates to a system and method of determining a differential state of a vehicle based on first and second wheel speeds.

A locking differential locks opposing wheels together such that the wheels rotate at the same speed. A locking mechanism moves from a first position in which the differential is unlocked, and a second position in which the differential is locked. When the locking differential is unlocked, a solenoid valve or a sensor detects that the locking mechanism is in the first position. When the locking differential is unlocked, the solenoid valve or the sensor detects that the locking mechanism is in the second position. The position of the locking mechanism is detected by the solenoid valve or the sensor to determine the operational state of the locking differential.

A need exists for a system and method of determining a differential state of a vehicle.

In view of the state of the known technology, one aspect of the present disclosure is to provide a control system configured to determine a differential state of a vehicle. The control system includes a first wheel sensor, a second wheel sensor, and an electronic controller. The first wheel sensor is configured to detect a first wheel speed of a first wheel. The second wheel sensor is configured to detect a second wheel speed of a second wheel. The electronic controller is configured to determine whether the first wheel speed is equal to or different from the second wheel speed, and to turn off an indicator when the first wheel speed is different from the second wheel speed. The indicator is illuminated to indicate a locked differential state of the vehicle.

Another aspect of the present disclosure is to provide a method of determining a differential state in a vehicle. A first wheel speed of a first wheel is detected. A second wheel speed of a second wheel is detected. A determination is made whether the first wheel speed is equal to or different from the second wheel speed. An indicator is turned off when the first wheel speed is different from the second wheel speed. The indicator is illuminated to indicate a locked differential state of the vehicle.

Also other objects, features, aspects and advantages of the disclosed system and method of determining an unlocked differential state of a vehicle will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the system and method of determining an unlocked differential state of a vehicle.

Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

1 2 FIGS.and 1 FIG. 10 12 14 16 12 18 16 16 10 Referring initially to, a vehiclehaving frameis illustrated in accordance with a first exemplary embodiment. Rear wheelsand front wheelsare rotatably connected to the framein a conventional manner. A steering wheelis conventionally connected to the front wheelssuch that rotation of the steering wheel causes pivotal movement of the front wheels. A forward direction and a rearward direction of the vehicleare indicated by the F and R directional arrows, respectively, in.

20 22 24 14 22 14 24 20 22 24 22 24 20 14 14 22 24 22 24 20 14 14 22 24 20 1 FIG. A differentialreceives a first rear axleand a second rear axle, as shown in. A first rear tireA is connected to the first rear axle. A second rear tireB is connected to the second rear axle. The differentialis conventionally connected to the first and second rear axlesandsuch that in a first, or unlocked, state of the differential, the first and second rear axlesandare not locked together. When the differentialis locked, the first and second rear tiresA andB rotate at the same speed because the first and second rear axlesandare locked together. In a second, or locked, state of the differential, the first and second rear axlesandare locked together. When the differentialis unlocked, the first and second rear tiresA andB rotate at different speeds because the first and second rear axlesandare not locked together. The differentialincludes a conventional locking mechanism configured to move between the locked position and the unlocked position.

26 20 26 28 10 2 FIG. 2 FIG. A differential state determination systemis configured to determine a differential state of the differential, as shown in. The differential state determination systemincludes an electronic controllerthat is connected to and/or is in electronic communication with various systems and components of the vehicle, as shown in.

10 20 28 28 28 26 28 28 28 28 28 26 28 26 The vehicleincludes a vehicle dynamic control (VDC) monitoring system control program. The VDC system is a conventional control system configured to maintain longitudinal and lateral stability of the vehicle. The electronic controllerpreferably includes a microcomputer that communicates with the VDC system. The electronic controllercan also include other conventional components, such as an input interface circuit, an output interface circuit, and storage devices, such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device and electronic storage devices or drives (all hereinafter referred to collectively as electronic memory). The microcomputer of the electronic controlleris programmed to control the vehicle dynamic control monitoring system and the differential state determination system. The memory circuit stores processing results and control programs, such as ones for the vehicle dynamic control monitoring system operations and the differential state determination systemthat are run by the processor circuit. The electronic controlleris operatively coupled to the various vehicle components and components of the vehicle dynamic control monitoring system in a conventional manner. The internal RAM of the electronic controllerstores statuses of operational flags and various control data. The internal ROM of the electronic controllerstores data communication protocols and commands for various operations. The electronic controlleris capable of selectively controlling any of the components of the control system of the vehicle dynamic control monitoring system and the differential state determination systemin accordance with the control program. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the electronic controllercan be any combination of hardware and software that will carry out the functions of the vehicle dynamic control monitoring system and the differential state determination system.

28 The electronic controlleris configured to perform a plurality of tasks and operations, and is programed to evaluate and process data from the various sensors and systems connected thereto, along with data relating to various on-road and off-road conditions, such as those described below.

10 30 32 30 14 32 14 30 32 30 32 22 24 30 32 14 1 FIG. The vehicleincludes a first rear wheel speed sensorand a second rear wheel speed sensor. The first rear wheel speed sensoris configured to detect a first wheel speed of the first rear wheelA. The second rear wheel speed sensoris configured to detect a second wheel speed of the second rear wheelB. The first and second rear wheel speed sensorsandare conventional sensors, and can be components of the VDC system. The first and second rear wheel speed sensorsandare preferably disposed at a wheel end of each of the first and second rear axlesand, as shown in, although the first and second rear wheel speed sensorsandcan be disposed in any suitable location to determine wheel speeds of the rear wheels.

30 32 28 30 32 28 The first and second wheel speed sensorsandare electronically connected to the electronic controller. The wheel speed detected by each of the first and second rear wheel speed sensorsandis configured to be transmitted to the electronic controller.

34 36 16 16 34 36 28 34 36 28 34 36 34 36 16 16 1 FIG. 2 FIG. First and second front wheel speed sensorsandcan be similarly disposed to determine wheels speeds of the first front wheelA and the second front wheelB, as shown in. The first and second front wheel speed sensorsandare electrically connected to the electronic controller, as shown in. The wheel speed detected by each of the first and second front wheel speed sensorsandis configured to be transmitted to the electronic controller. The first and second front wheel speed sensorsandare conventional wheel speed sensors. The first and second front wheel speed sensorsandare preferably disposed at a wheel end of the front axles, although the first and second front wheel speed sensors can be disposed in any suitable location to detect the wheel speeds of the first and second front wheelsA andB.

18 16 16 18 16 16 38 18 38 28 18 28 38 The steering wheelis operatively connected to the first and second front wheelsA andB to transmit rotational movement of the steering wheelto the first and second front wheelsA andB. A steering wheel sensoris conventionally mounted, such as fixed onto a steering column, to detect a rotation, or steering, angle of the steering wheel. The steering wheel sensoris electrically connected to the electronic controllerto transmit a detected steering angle of the steering wheelto the electronic controller. The steering wheel sensoris a conventional steering angle sensor.

26 40 42 40 10 40 42 42 44 2 3 FIGS.and The differential state determination systemcan further include a displayand an instrument cluster, as shown in. The displaycan be a video monitor or touch screen display installed to an instrument panel within the passenger compartment of the vehiclein a location easily observed by the vehicle operator. The displaycan be part of the instrument clusteror can be installed at a location spaced apart from the instrument cluster, such as part of the infotainment system.

42 46 48 50 52 50 50 50 40 42 52 20 52 20 10 52 46 40 42 28 3 4 FIGS.and 3 4 FIGS.and 3 4 FIGS.and 2 FIG. The instrument cluster, as shown in, includes a speedometer, a tachometer, a first lamp, and a second lamp. The first lamp, or indicator,is illuminated in response to the four-wheel drive (4WD) system being activated. As shown in, the first lampis illuminated to indicate that the four-wheel drive system is in the 4WD low (4WD LO) setting. The first lampcan be disposed in any suitable location, such as on the displayof the instrument cluster. The second lamp, or indicator,is illuminated to indicate that the differentialis in the locked state. As shown in, the second lampis illuminated to indicate that the differentialis in the locked state (e.g., “DIFF LOCK”). In other words, the second lamp is illuminated to indicate a locked differential state of the vehicle. The second lampcan be disposed in any suitable location, such as on the speedometer. The displayand the instrument clusterare electrically connected to the electronic controller, as shown in.

42 54 54 50 10 3 4 FIGS.and The instrument cluster, as shown in, includes a four wheel drive (4WD) knobthat is operated to control an operational mode of the 4WD system. The 4WD knobis operable to set a two-wheel drive, a 4WD high, and a 4WD low state of the 4WD system. The first lampis illuminated to indicate the current 4WD operating state of the vehicle.

42 56 20 14 14 14 14 56 20 56 20 52 20 50 42 56 16 16 56 58 3 4 FIGS.and 1 FIG. 3 FIG. The instrument cluster, as shown in, includes a locking differential switch, or button,that is operated to cause the differential() to lock the first and second rear wheelsA andB such that the first and second rear wheelsA andB turn at the same speed. The locking differential switchis pushed to lock the differential. The locking differential switchis pushed again from the locked differential state to unlock the differential. The second lampis illuminated to indicate the locked state of the differential. The second lampis not illuminated when the differential is in the unlocked state. The instrument clustercan include another locking differential switch that functions substantially similarly to the locking differential switchto cause another differential to lock the first and second front wheelsA andB. The locking differential switchcan be disposed in any suitable location of a dashboard, as shown in.

20 28 28 52 22 24 20 16 16 The detected first wheel speed is compared to the detected second wheel speed to determine the differential state of the differential. The electronic controlleris configured to determine whether the first wheel speed is equal to or different from the second wheel speed. Preferably, the first and second wheel speeds are compared over a predetermined amount of time, such as 0.5 seconds, to substantially prevent an instantaneous false positive. In other words, comparing the first and second wheel speeds for a difference over a predetermined amount of time substantially prevents an instantaneous wheel speed difference being indicative of the differential being unlocked. The electronic controlleris configured to turn off the second lamp, or indicator, when the first wheel speed is different from the second wheel speed. The first wheel speed being different from the second wheel speed indicates that the first and second axlesandare not rotating together, such that the differentialis in the unlocked state. A difference in wheel speeds between the first and second rear wheelsA andB can occur during, but is not limited to, wheel slip (e.g., when a driver hits the throttle hard) or when turning (e.g., left or right).

10 28 26 14 14 10 56 20 56 20 12 56 20 14 5 FIG. During operation of the vehicle, the electronic controllerof the differential state determination systemis configured to monitor the first wheel speed of the first rear wheelA and the second wheel speed of the second rear wheelB in accordance with the flowchart shown in. In step S, the system determines whether the locking differential switchis being pressed to engage or disengage the differential. When the locking differential switchis pressed to engage the differential, the process moves to step S. When the locking differential switchis pressed to disengage the differential, the process moves to step S.

12 28 16 18 5 FIG. In step Sof, the electronic controllerdetermines whether the 4WD operational mode is in 4WD low (i.e., 4LO) and whether the vehicle speed is 0 mph (i.e., whether the vehicle is not moving). Alternatively, any suitable vehicle speed, such as 6 km/h) can be used to set the 4WD low mode. When both of these conditions are not met, i.e., either the vehicle is not operating in 4WD low or the vehicle speed is not equal to or less than the predetermined vehicle speed, the process moves to step S. When both of these conditions are met, the process moves to step S.

16 52 20 10 5 FIG. In step Sof, the second lampis not illuminated because the conditions have not been met to lock the differential. The process ends, and returns to step S.

12 28 18 18 20 20 5 FIG. In step Sof, when the electronic controllerdetermines that the 4WD operational mode is in 4WD low and that the vehicle speed is 0 mph, the process moves to step S. In step S, the locking mechanism of the differentialis energized to move the differential to the locked state. The process moves to step S.

20 28 38 28 10 22 5 FIG. In step Sof, the electronic controllerdetermines the steering angle from the information transmitted by the steering angle sensor. When a steering angle is not detected (i.e., a steering angle of zero is detected), the electronic controllerdetermines that the vehicleis traveling straight, and the process moves to step S.

10 14 14 10 24 When the vehicleis traveling straight (i.e., a zero degree turning angle), the first and second rear wheelsA andB rotate at the same speed. When a steering angle is detected (i.e., a non-zero value), the vehicleis determined to not be traveling straight, and the process moves to step S. With a non-zero turning angle, the inside wheel rotates more slowly than the outside wheel due to the shorter radius being traveled by the inside wheel, thereby being indicative of the first and second wheel speeds being different.

22 52 20 5 FIG. In step Sof, the second lampis caused to flash to indicate that the differential is in the process of engaging but is not yet in the locked state. The process moves to step Sto determine the steering angle.

24 28 30 32 10 24 28 56 58 22 52 22 24 20 20 28 52 56 24 5 FIG. When a steering angle is determined, the process moves to step Sof. The electronic controllercompares the first wheel speed and the second wheel speed based on information transmitted by the first rear wheel speed sensorand the second rear wheel speed sensor. In other words, as shown in step Sand S, the electronic controlleris configured to determine whether the first rear wheel speed is equal to or different from the second rear wheel speed responsive to the locking differential switchon the vehicle dashboardbeing pressed. Preferably, the first and second wheel speeds are compared over a predetermined amount of time, such as 0.5 seconds, to substantially prevent an instantaneous false positive. When a difference between the first wheel speed and the second wheel speed over the predetermined amount of time is a non-zero value, the process moves to step Sin which the second lampis caused to flash. A difference in the first and second wheel speeds indicates that the first and second axlesandare not locked together, thereby indicating that the differentialis not yet in the locked state. The process returns to step Sto determine whether a steering angle is detected. In other words, the electronic controlleris configured to flash the second lampafter the locking differential switchis pressed until the first rear wheel speed is determined to be the same as the second rear wheel speed (step S).

28 24 26 22 24 14 14 26 52 20 10 28 52 56 20 14 5 FIG. When the electronic controllerdetermines there is no difference between the first wheel speed and the second wheel speed in step S, the process moves to step S. Determining that there is no difference between the first wheel speed and the second wheel speed indicates that the first and second axlesandare locked together as the first and second rear wheelsA andB are rotating at the same speed. In step S, the second lampis illuminated to indicate that the differentialis in the locked state. The process then returns to step S. The electronic controlleris configured to maintain the second lampin the illuminated condition when the first rear wheel speed is the same as the second rear wheel speed until the locking differential switchis pressed to disengage the differential, as shown in step Sof.

10 56 20 20 14 14 20 28 28 38 28 10 30 10 32 5 FIG. In step Sof, when the locking differential switchis pressed to disengage the differential(i.e., when the differentialis in the locked state), the process moves to step S. In step S, the electronic controller de-energizes the lock mechanism of the differential. The process then moves to step Sin which the electronic controllerdetermines the steering angle from the information transmitted by the steering angle sensor. When a steering angle is not detected (i.e., a steering angle of zero is detected), the electronic controllerdetermines that the vehicleis traveling straight. The process moves to step S. When a steering angle is detected (i.e., a non-zero value), the vehicleis determined to not be traveling straight, and the process moves to step S.

30 52 28 5 FIG. In step Sof, the second lampis caused to flash to indicate that the differential is in the process of disengaging but is not yet in the unlocked state. The process returns to step Sto determine the steering angle.

28 32 28 30 32 16 52 22 24 20 16 52 20 28 32 28 52 28 32 16 10 28 52 56 32 5 FIG. When a steering angle is determined in step S, the process moves to step Sof. The electronic controllercompares the first wheel speed and the second wheel speed based on information transmitted by the first rear wheel speed sensorand the second rear wheel speed sensor. Preferably, the first and second wheel speeds are compared over a predetermined amount of time, such as 0.5 seconds, to substantially prevent an instantaneous false positive. When a difference between the first wheel speed and the second wheel speed is a non-zero value, the process moves to step Sin which the second lampis caused to turn off. A difference in the first and second wheel speeds indicates that the first and second axlesandare not locked together, thereby indicating that the differentialis not yet in the locked state. The process moves to step Sto turn off the second lampto indicate the differential is in the unlocked state. In other words, the locking differential state determination system determines that the differentialis in the unlocked state based on a detection of a steering angle (step S) and a comparison of the first and second rear wheel speeds (step S). The electronic controlleris configured to turn off the second lampwhen the steering angle is a non-zero angle (step S) and the first rear wheel speed is different from the second rear wheel speed (step S). From step S, the process returns to step S. In other words, the electronic controlleris configured to flash the second lampafter the locking differential switchis pressed until the first rear wheel speed is determined to be different from the second rear wheel speed (step S).

28 32 30 22 24 14 14 30 52 20 52 28 When the electronic controllerdetermines there is no difference between the first wheel speed and the second wheel speed in step S, the process moves to step S. Determining that there is no difference between the first rear wheel speed and the second rear wheel speed indicates that the first and second axlesandare locked together as the first and second rear wheelsA andB are rotating at the same speed. In step S, the second lampis caused to flash to indicate that the differentialis not yet in the unlocked state. In other words, the flashing second lampindicates that the differential is transitioning from the locked state to the unlocked state. The process then returns to step Sto determine whether a steering angle is detected.

5 FIG. 26 20 The locking differential state determination system illustrated inis applicable to any opposed pair of wheels configured to be locked together by a differential. The locking differential state determination systemdetects a differential state of the differentialbased on a comparison of first and second wheel speeds without requiring an additional sensor or solenoid valve configured to detect a position of the locking mechanism.

In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Also as used herein to describe the above embodiment(s), the following directional terms “forward”, “rearward”, “above”, “downward”, “vertical”, “horizontal”, “below” and “transverse” as well as any other similar directional terms refer to those directions of a vehicle equipped with the system and method of determining an unlocked differential state of a vehicle. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a vehicle equipped with the system and method of determining an unlocked differential state of a vehicle.

The term “detect” as used herein to describe an operation or function carried out by a component, a section, a device or the like includes a component, a section, a device or the like that does not require physical detection, but rather includes determining, measuring, modeling, predicting or computing or the like to carry out the operation or function.

The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.

The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired.

Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.